Does my sister-in-law count as a relative?

My eligibility for naturalisation is quickly approaching, and I'm starting to think about rounding up potential referees.
The easiest person to ask who has a professional standing would be my sister-in-law. She is the woman who is married to my husband's brother. Does she count as a relative? I suppose she does share the last name, so it might be complicated to explain.

I can ask my supervisor, who is a Doctor, but our acquaintance will be two months shy of the three year requirement when I am finally eligible to apply.

Unless WebyJ or someone else with more knowledge contradicts me, I would say that your sister-in-law counts as a relative, so you won't be able to use her as a referee.  Don't forget teachers and social workers count as professional status.  Do you know any?

Any thoughts on whether DH's brother's fiancee would count as a relative?  I was thinking along the same lines as across, although I do know teachers they are EFL teachers in a private language school, not proper schoolteachers.  Would they still count?

Do you know anyone in the US who would meet the criteria?

I would say that inlaws, even ones that are married to inlaws, wouldn't count because the form says you can't use someone who is related by marriage.  We didn't even use my SiL's (sort of ex) partner because even though they aren't married and not really in a relationship at them moment, he is sort of related to my relations through their kids.  I wouldn't use a fiancée either, even though it might be technically not excluded, it sort of goes against the spirit of what they want, as dated and meaningless as what they want is.

Malcolm's spot on.  You can use referees from the US (or someone of any nationality) for the professional one.

You could also wait the 2 months until your supervisor is eligible.  Presumably, you have ILR, so there isn't necessarily a strict deadline that you need to apply by.  It might just be easier?

You could also wait the 2 months until your supervisor is eligible.  Presumably, you have ILR, so there isn't necessarily a strict deadline that you need to apply by.  It might just be easier?

Yes, plan B is just to wait. I know lots of folks in the US, but not sure it's worth the effort of mailing the forms over to get signed just to complete things a month sooner.