If you're looking to have kids without the need for a pregnancy, then you can use the adoption option in BitLife to create a family! This is a pretty easy process, but there's a couple things you should know before taking the plunge.
To adopt a kid in BitLife, you will need at least $20,000 and own a home. Each kid has a different price that you need to pay to adopt them, and you can't adopt a child without owning some property!
You have to be 18 or over to get the adoption option available to you. To find it, just go under the Activities tab and then look for Adoption. You will get a selection of 5 - 6 kids, and each one has a different behavior rating. I haven't found that it mattered too much, I've gotten kids with red ratings and they didn't really do anything different. It is likely to do with their stat distribution. When you select a kid you will see the amount of money it will cost you to adopt them. You will also find out if the kid is from a foreign country or not, if there's a listing under Birthplace. This is important for certain challenges in BitLife.
Before you can adopt a child, you will need to own a home. Go to the Assets menu, and then Go Shopping. Look for the Real Estate Brokers and go ahead and look through the homes you can purchase. If you don't have a lot of money, you can always apply for a mortgage. You will then be charged each year until it is completely paid off or you sell the home.
That's really all there is to it on adoption in BitLife! If you have any questions, let me know in the comments.