Philip, my younger child, started seeing a girlfriend during the holidays.  They went to the movies a couple of times as well as to lunch. I was a little concerned that my older son, Matthew, would tease Philip about Tara and try to embarrass him. Much to my surprise he didn't. 

I mentioned this at the workshop and Robin asked me whether I'd let Matthew know that I had noticed his behaviour. I decided to write him a note, praising him, which I did.  I've just gone and got the note out of his box where he keeps special things - he still has it 3-4 months later.

Dear Matthew.    Since Tuesday - Philip and Tara’s date - I've been thinking a lot about how well you handled this 'new situation'. I wanted to tell you that I noticed how you gave Phil the opportunity to be with Tara without interfering. I have also noticed that since the date has happened, you've once again not intruded on his friendship with her.  You've behaved in a very understanding and mature way and I wanted you to know that I've noticed your behaviour and I've been feeling very proud of your maturity.  It can be tough growing into a young man. This is certainly an excellent beginning.  

Thanks Maths.
love Mom   xxxx

This note had a profound effect on Matthew - he suddenly became more sure of himself - not in a cocky way - but in a quietly confident way. He acknowledged the note with a smile and we have never discussed it, but it was one of the most positive interactions I've had with him.