DSD will be 12 when peanut is born - and yeah, it's not how I would have planned it, but I am the oldest of 4 - with 4 years between me and my first brother, 6 years between me and my sister and 18 years between me and my baby brother - it's been fine and in fact the 18 year gap is great - weird, but I love him like my own.

A family evolves and changes and develops with each new member - I think you are right to come to the decision that it doesn't matter. What will be will be. There are good things and bad things whatever the age gap