Mums with 2+ children

How did you deal with your first not being an only child anymore ? I’m kind of struggling that my son won’t be an only child, I have days where I’m in tears because of it, I’m doing a lot of me and him time lately. I know he will be a good big brother (he will be almost 5 when baby girl arrives), he’s always been around babies and always likes helping out with them. I’m just struggling with the fact that when she’s here most of my time with llll be all about the baby, and of course I’m going to involve him in a lot of things and I’m still going to try and still have our time together. How did you mummy’s cope ?