why are you acting like its amatonormativity that forces people to want to live with their spouse? unironically romantic attraction just makes most people want that. like would i rather live in the same house as the person i really enjoy sleeping next to, have sex with, feel ok being naked in front of, and the person i love just being able to hug or cuddle any time.... or my cousin and have to ration shower time, stress about where to take my dates, etc.
I think this ask is actually effective at pointing out a couple aspects of amatonormativity that put aroace people at a systemic disadvantage when they're perpetuated. I'll go ahead and identify them here under the assumption that this ask is in good faith.
For clarity's sake, I'll start it off with the definition of amatonormativity: "the set of societal assumptions that everyone prospers with an exclusive romantic relationship" (from Wikipedia, emphasis is my own).
"Romantic attraction makes people want to live with their spouse" is indeed a generally true statement, and semantically speaking, this statement is not, by itself, inherently amatonormative.
However, this ask proposes an "either/or" situation in which living with one's spouse or living with one's cousin are two mutually exclusive scenarios; the statement about wanting to live with someone you're romantically involved with becomes amatonormative when you introduce the assumption of exclusivity, i.e. that living with your spouse necessarily means that you cannot also live with your cousin.
In reality, very generally speaking, there is no rule preventing a married person from living in a household that includes both their spouse and their cousin (or other cohabitant[s]). A lot of times, people just don't, because under amatonormative societal expectations, that scenario isn't even presented as a possibility. Cohabiting with someone who's not a romantic partner is widely seen either as a last resort or as a short-term arrangement, while, conversely, exclusive cohabitation with a romantic partner is set as a long-term goal that's allegedly preferable to any other possibility. So with some logical deductions, you could see how this would be disproportionately harmful to people who don't have or want a romantic partner.
It should go without saying that, in any real-world situation, there's a lot of practical factors that come into play regarding cohabitant compatibility and such. However, said factors apply to any relationship, not just a specific type. Interpersonal relationships involve communication, setting expectations, and solving problems, regardless of who they're with. People will necessarily get along better with some other people and not as well with some other people.
Inversely, it's entirely possible for people to be in a situation where they get along worse with their spouse than they do with their cousin, or indeed, anyone who's not their spouse. It's far from uncommon for people to end up in situations where they're married to someone who objectively sucks. (And/or maybe their cousin is legitimately just that awesome of a person!) Speaking personally, I have plenty of examples in my workplace alone, not to mention people I know second- or third-hand, of people in this exact situation, for a wide variety of reasons, including sheer societal pressure -- that is, subscription to the belief that everyone prospers married.
All too often, it ends up in a kind of logical loop of them believing that, because their relationship is romantic in nature, it must necessarily be more mutually beneficial than their other relationships -- which is not always the case, and they end up gravely overestimating just how good the relationship actually is for them.
Again, there are as many possible outcomes as there are individual situations in the world; likewise, without knowing way more details about your interpersonal relationships than necessary, I can't make any definitive assessments or judgment calls about the nature of your compatibility or lack thereof with someone -- so I say this more as a precaution than anything else: the generalized belief that relationships with a spouse are inherently better, that they're higher in priority and more exclusive, than those with a cousin or anyone else, is a defining factor of amatonormativity.
So, to bring it back to the original ask: yes, romantic involvement can and often does make you want to live with someone. However, romantic involvement is not a prerequisite to cohabiting, nor does cohabiting necessitate a romantic relationship, nor does romantic involvement alone necessarily guarantee long-term compatibility as far as cohabiting goes.
The first statement alone is not inherently amatonormative. Factor in the latter three assumptions, though, and boom, you have amatonormativity and its general effect on housing situations in a nutshell.