A long time ago, someone said “You can’t pick your family, it’s genetics”. In many cases that is very true. It’s hard to argue with biology. You cannot alter who gave birth to you. But sometimes, “family” can be much more than biology or marriage.
Probably almost everyone has had the childhood experience of being parented by the parents of a best friend. Occasionally, over time, a bond builds between people and that bond feels as least as strong as biological family. That’s just the way things work out sometimes.
As adults, one may have had the experience of making a friend that becomes so close as to feel like family. You may even start to refer to each other with family titles (brother, sister, cousin, etc.). These bonds form within various contexts, like school or work, and may even overcome the hindrance of distance to allow for regular “reunions”.
It does not matter so much who you draw close, but that you do draw others close. As humans there is a need for connections with others. There are times when it is impossible to “go it alone”. The human psyche can be strong enough for the day-to-day but that strength needs to be refreshed occasionally with the contact of those who understand you best. And many times, those who understand us best are those we have chosen as our “non-biological family”.