I'm really worried about DH's behaviour lately and for a while now. We have 3 daughters, 10, 8, and 4. He takes them to school everyday as he catches the train in the same location. I was aware of him talking to one of our 4 year old's mums every now and then but now it seems like it's an every day occurrence and they have become very friendly, messaging on FB, etc. He also never speaks to anyone else. This leaves me feeling uneasy as DH doesn't have a lot of friends and in the 20 years I've known him he has never had a female friend, only work colleagues.
Anyway, they both have started the same hobby recently and have agreed to start going together. DH knew that I wouldn't be comfortable with it but said that if I said he shouldn't go then I would be ruining it for them and it would be my fault 
I feel really uneasy about the whole friendship as DH seems very emotionally invested in the friendship. He's the type to be very flattered by attention and just worried that he really is playing with fire.