I would really caution him to ask someone he is closer to, even if it means a relative. This is my second wedding and I was kind of in his shoes at my first. I had 4 bridesmaids that I kind of scrounged up. One was my sister- still talk to her. One was my sister in law- talked to her until the divorce, and two were girls I had been hanging out with as a single chick, who I had lost contact with within a year of the wedding. I always felt bummed about that, because these are supposed to be people who will support me through life’s trials- and I excluded one sister to include them- and they were never there for me. Not that they were bad chicks, we just didn’t have much in common besides wanting to go out on Friday nights.
This time even though I have two sisters and one best friend, I’m having my two teenaged sons stand up with me. FH is having two friends, and I don’t think it’s an issue that they are coming from different parts of our lives.
If he doesn't feel like he's close enough to the guys in his life to ask them to be groomsmen, I wouldn't force it. It's totally ok to have an unbalanced bridal party! In that case your girls could walk up the aisle and sit in the front row (rather than stand next to you) if you're worried about photos looking uneven or weird. The important thing is to surround yourself with the people that you are closest to at this point in your life!
I was the one with not many people I wanted to have and he wanted 4. Thus, I asked my sister, my cousin, my nephew's mom, and my brother's gf. I'm nervous about having my brother's gf as I'm not super close with her, but even if they break up after the wedding, it's just some photographs, and me having her in it stops any drama from my brother!
I'd say try to stick with family (cousins, uncles, siblings, etc) because they tend to always be in your life even if you aren't super close! Also, uneven sides is totally fine - I just couldn't do it because I need it to look even (it's all dependent on how you two want it to look). Good luck!
I mean I would recommend not doing a formal bridal party, but if you have your friends who you want to be a special part of your big day you can still do it without giving out formal titles or anything like that. I'm sure your friends will understand and still be honored to be a part of your big day without a title.
I dont have a lot of friends either, mine are mostly family. My FH has 6 groomsmen but I decided my parents will stand beside me after walking me down the aisle and we probably are also not making them stand in line, just having them spread around nearby. People who are close to us and special to our lives.