Is it appropriate/wise to include personal/family reasons in a "Justification for Choice of Host" on a fellowship application? I am applying for a fellowship that would allow me to start an independent research group--something between post-doc and faculty levels.  Part of this application requires that I explain my choice of host university.  My question is whether I should include family reasons alongside professional ones in my justification statement.

The university I'm hoping to work at is strong in my general field, though the academic fit could be a bit better (e.g. more faculty with complementary interests, more labs with relevant equipment/resources I could use).  The main reason I'm choosing this university is because of family reasons: my partner has a good job at this university already, and since we have a small child together, I can't reasonably move elsewhere without totally disrupting my entire family.

After hitting the standard points (the strengths of the university and department, relevant faculty interests, professional development opportunities), should I also mention my family situation?

On the one hand, I'm worried that some reviewers might find it inappropriate for me to include personal asides.

On the other hand, I think including this aside is a good place for explaining why I have a bit of a gap in my CV (I took family leave and am looking to return to academics), and why I'm choosing a place that the reviewers may think isn't ideal.  My CV mentions that I took family leave, but of course this small line item could easily be missed.  I'd normally use my cover letter to explain my situation, but in this case cover letters get stripped before the application reaches the reviewers.

If it's relevant, this is in the UK, in the natural sciences.  

Thanks!
I've been involved in a few searches where this issue has come up. Sometimes it helps the candidate, sometimes not so much.

When it helps: In trying to decide whether to bring a highly competitive candidate to campus for an interview. No one wants to go to the trouble and expense of an on-campus interview for a candidates who isn't going to accept an offer. Knowing that a candidate has compelling personal reasons for wanting to live in the area makes it much more likely that a seemingly over-qualified candidate will be taken seriously. 

When it hurts: Any time it looks like location is the primary reason the candidate wants the position. It's great that folks want to live and work and retire in our town; it's not great if they're willing to take a job they don't particularly want in order to accomplish that. It's even worse if they aren't able to speak to the specifics of their "fit" with the institution much beyond "I really want to work here".

In your particular case, I'm not sure that there's any upside of sharing this information. Your reviewers are already going to know that out of all the host universities you could possibly choose in the world, this is the one you prefer. What they don't know is why this is your first choice. If they learn that it is due to your spouse's location, they may wonder what would happen if your partner gets a different job, or your relationship hits a snag. Those who sympathize with the host institution may also feel that it deserves someone who loves it for itself, so to speak. It will be better for you if they believe simply that it is because you feel that this is the place where you can do your most brilliant work—which is probably true, as it's hard to be brilliant when your home life has been turned upside down—for a variety of reasons including your "standard points". At most you might want to say that you are familiar with the institution, and feel comfortable there.

As far as signalling why you have an employment gap—are you submitting letters of recommendation? If so, perhaps one of your references could speak to this issue. That was how I handled my own parenting-related employment gap when I returned to the workforce.