I think it will have an impact on how many you have. Infact I think siblings have a huge impact on your life one way or another.
I had 1 brother 5.5 years older than me.
His jealousy of me made my life a total nightmare. He hated my existance and I have no memory of ever playing together or doing anything together. He left home and joined the Royal Marines when I was 11.5.
As a result, not only did I live the life of an only child but I was bullied by the one sibling I did have.
My dad was a bully so I now have no contact with either my dad or my brother.
My DH is the youngest of 4. He has 3 older sisters. The 2 older ones kind of mothered him but the younger sister was a definite 'middle child' and drove my DH mad.
They are all close now.
I look at myself with only my mum around (who can be hard work) and then I look at my DH with 3 sisters, a mum & dad, 3 neices and a nephew and think how lucky he is.
He is a more grounded happy person than me too.
I have one DS and one DD with 2.7 years between them.
I had a horrendous PG and birth with serious risks with DS.
Even though the thought of going through it again, especially so soon made me physically ill, I forced myself to have another.
Im glad I did although I get really really OTT and upset when DS is jealous and hits DD and trips her up. It pushes my buttons and it's this very reaction that is going to drive a wedge between them if I don't get a grip
. Trying hard though.
I still feel my family is too small. Im TERRIFIED something happens to one of them.
I read a poster on another page of this thread (sorry I didn't remember your name) who had grown up close to her brother and he died 4 years ago 

. I felt so bad for her and it's a huge fear that one of them suddenly becomes an only child (totally irrational I know).
I keep thinking maybe I should have a third but I now have mild health issues after my PG and the high risk factor and also my 2 were early. I make myself so stressed thinking about going through it all again but this irrational fear of having a small family and my DC's feeling lonely eats away.
Wow, im more messed up than I previously realised
.