My mother is a single parent, and so I have been brought up without a male parent. Am I deeply traumatised? No.
Children honestly never learn
anything about the 'Facts of Life' from their parents. As Abby said, children mostly learn from older friends, or, failing that, by trial and error...

But seriously, I have never had any problems with lacking a male influence in my family, and I can see no reasonable reason why gay couples should be denied the joy and pain of raising a child. Anybody who disagrees is welcome to; it's been a while since I've had a good row...
