It’s well-documented that having siblings (or not having siblings) can affect everything from your personality to your mental health. But, if you’re a woman, can having sisters affect whether or not you have a lot of friends?

One woman on TikTok, Brittney Nicole, seems to think so. She recently shared a theory about why she only has a couple of really good female friends: It’s because she already has sisters.

“I strongly believe if you have sisters you are less likely to have more friends,” she begins. “Because you already have people to stand up at your wedding on your side. You already have people you trust. You already have people to be at your family events — because they’re family. You love them. You trust them. They’re similar to you a lot of the time.”

She adds that having siblings has made her more careful when it comes to letting other people into her life, too.

“I’m so selective with friends because I have my sisters,” she goes on. “I don’t feel like I need to have a lot of friends. There’s just no reason to have other friends in my life unless I feel like they are really good people and they add value to my life and I add value to theirs.”

Why have a ton of friends, anyway?

“I don’t need 45 other friends,” she concludes. “I have my core three sisters and then maybe one or two other friends.”

Down in the comments, a lot of people thought she was spot on.

“I feel like my friends just can’t live up to the standard of my sister,” one person shared.

“As someone who has a sister and mom as my best friend, I’m super selective with my friends and I’ve dropped people as soon as they become bad friends,” another shared.

“There will never be a social situation where you can be so unapologetically yourself as you can in a sister situation. It’s effortless,” said another.

“I always thought this and wondered why I didn’t have very many and my mom said, ‘It’s because your sisters meet all your needs’,” another person shared.

So, does science back up this theory? While I couldn’t find any studies about the direct topic of people with sisters having fewer non-familial close friendships, there has been research done about the strength of sisterhood.

Specifically, the sister bond is one of the strongest, closest, and longest-lasting relationships that exists. And a 2020 study found that strong sister-sister relationships can increase confidence and self-love while offering lifelong companionship. Another study showed that people with a close sister are more independent and goal oriented, which also supports the above theory that they might not need a huge entourage to feel satisfied and get things done. The same study found that just having a sister living nearby increases happiness.

In other words, while we can’t quite say that people with sisters don’t need or have many other close friendships, we can say that most of the time, having sisters makes our lives better and they often come as built-in besties for life.