What this post aims to do is provide an in-depth look at the
progression of Spain and Romano’s relationship over their life courses.

Early Guardianship:

The two got off to a rough start when
Spain conquered South Italy. Romano, who already had trust issues stemming from
the twofold sword of having Rome focus all his attention on rearing Veneziano and
later dying without much warning, has these issues exacerbated by his early
relationship with Spain.

Sources: Hetarchive, Chibitalia & Volume 6. 

Spain wishes that he had received Veneziano
instead and begs Austria to trade Italy brothers with him. I attribute the
crudeness of this to the fact that it was very early on in the series, but canon
material is canon material; it must be worked with. Of more importance is the parallel of coming second to Veneziano. 

Source: Hetarchive, Boss Spain’s Control of Southern Italy.

Essentially, Romano develops an inferiority complex and
feels inadequate in comparison to Veneziano. He can’t cook, he can’t clean, and
he has no manners. I mention this because it acts as a backdrop for Romano’s
initial hostility towards Spain.

Source: Hetarchive, Boss Spain’s Control of Southern Italy pt. 2.

Even as Spain gives him the best care possible, Romano
denies the reality and states otherwise. Being cared for is foreign to him, so
the hostility didn’t just emerge in a vacuum. He’s distrustful and confused. Or
perhaps he’s even testing Spain by lashing out, seeing how much the latter can
handle.

Source: Volume 4. 

Point is, there’s a degree of skepticism that makes sense
and it would be too simplistic to portray Romano as an entitled brat given what
he experienced in his early childhood.

Ex: Spain resorts to wearing rags and funds a whole new
wardrobe for Romano. Notice how the blush on Romano’s face (embarrassed, surprised
and flattered) betrays his true emotions rather than his hostile remark.

Source: Volume 4.

The next strip is particularly important in resolving this
sense of devaluement that Romano felt.

The frustration was mostly felt in how Romano didn’t live up
to Spain’s expectations, as he was held up to a measuring rod that reflected
Veneziano’s qualities. In other words, Romano wasn’t being valued as his own
person by Spain.

It was only until Spain learned to value Romano for his own
unique qualities and positive character traits that the two came to an
understanding.

This occurred when Romano perceived a troop of German
soldiers that Spain had allied with to be enemies. To Spain, Romano’s tantrum is
childish…but that’s because he is a child. In Romano’s world, Spain was in
danger, and he was willing to sacrifice his life for him. That’s why Romano
becomes angry with Spain and throws another fit when he’s reprimanded.

Source: Hetarchive, Boss Spain Doesn’t Understand.

The two take some time to cool off and Spain realizes that
even though Romano perceived the situation incorrectly, he had good intentions.
The message conveyed at the end of this strip– titled Boss Spain Doesn’t Understand–entails Spain learning to step into Romano’s world and understand
his way of viewing things. By doing so, Spain was able to appreciate Romano for
who he is rather than who he’s not.

In another strip, Romano shows his appreciation for the financial sacrifices Spain made for him, by deciding to sleep with the latter. Of course, it’s very Romano-esque, resulting in Romano taking over Spain’s bed. What’s touching is that Spain understands that Romano is trying to convey his thanks and accepts it as is. 

Source: Boss Spain’s Control of Southern Italy pt 2.

Late Guardianship:

Although this is a brief and shallowly covered period of
their relationship, we know that the two lived comfortably and peacefully
together.

Spain sees Romano grow up from a young child, to a child,
and to a late teenager.

Source: Hetarchive (Bamboo Thicket, eng trans., Feb 6th, 2015). 

There’s even an arc where Spain passes down his medieval
chivalric romance novels to Romano, who goes through a nerdy middle school
phase with them.

Source: Hetascanlations, World Stars Chapter 279. 

While long-lasting and cordial, the stable environment
Romano had found in Spain’s home ended abruptly upon Italian Unification, where
he was forced to live with his brother after centuries of separation.

Source: Hetascanlations, World Stars Chapter 73. 

It’s not so much that this creates a break in Spain and
Romano’s relationship, but as I’ll get into in the next section, it creates a
bit of a grey area for them regarding how they navigate the shift from a
guardian-child relationship to simply being friends.

Post-Guardianship:

Regardless of the fact that their guardian-child relationship
ceased to exist, Spain and Romano still relied on each other. They were and remain
as each other’s support systems.

Ex: When Romano moves to America for work during the Second Industrial
Revolution – a foreign and unfamiliar place–his first thought is to call
Spain.

Spain is still home in his mind, and home brings comfort.
Notice how it’s stated that Romano is closer with Spain than he is with his own
brother ↑

Source: Hetascanlations, World Stars Chapter 73.

The irony of their relationship is that even though Spain
has learned to understand Romano – such as seeing through his hostility – he still
remains oblivious at times. In other words, they either click and are on the same
wavelength, or they completely misunderstand each other, echoing the Boss Spain Doesn’t Understand comic.

Source: Hetascanlations, World Stars Chapter 75. 

Either way, the reliance hasn’t gone away.

Ex: Spain takes a drunk Romano home after the Halloween
2013-2014 event.

Source: Hetarchive, Halloween 2013-2014 Event.

What’s new in this phase of their relationship, however, is
that Spain can also rely on Romano.

Ex: Romano saves Spain with imports during an economic
crisis. He even faces off against the mafia, whom he’s normally terrified of.

Source: Hetarchive, In just two minutes you can grasp the exterior of the European Economy. 

That said, I think the “grey area” in Spain and Romano’s
relationship has a lot to do with the fact that they’ve worked away from the
guardian dynamic and yet haven’t exactly defined how they should go about their
friendship.

Source: Volume 5.

Although, Spain certainly has become very fond of Romano and
has a habit of stepping over his boundaries…

Sources: Volume 2 & Hetarchive (Bamboo Thicket, eng trans., Dec 5th, 2014 & Nov 6th, 2013).