Help me honor my sister please!

So my boyfriend and I have had it pretty rough throughout our relationship. His mom passed away a couple of months after we started dating. I never really got a chance to know her and I hate that every day. Her middle name was Mae, so we plan on honoring her by using it for a daughter if/when we have one. Well, my sister, Emily, passed away a few months after her and I planned on naming my daughter Emma to honor her. I had it all planned out, so excited to one day have my sweet Emma Mae, honoring two very important people to me and the love of my life. HOWEVER, his cousin ended up having a daughter (super freaking adorable) and she named her Emma and he says we shouldn't use that name because we don't want her being "the other Emma" of the family. Not only that, but Emma is, I believe, the number one girl's name in the country and I don't want her to be "Emma B." in school. My question is how do I honor my sister with my baby girl's name? I don't want to just use Emily becauae I want her to kind of have her own name. Or even if i have a son, a way to honor her with a boy's name? My dad passed away a month after my sister and we plan on using his middle name for a boy, which is Ray, so keep that in mind if you have a name for a boy! Thanks everyone!