Thank you all who have given me advice......

I have just had both of them out at the same on the bed in my spare bedroom, ok they were not exactly playing with each other, but they were not fighting......

Except one little incident which was more like a rat head butt and a stare from the older rat and a little squeak from the younger one.......

Apart from that I was just happy to see them not in their own cages and interacting a little....... I know it might take a while but to me this is one little step forward.......

Again thank you all....... will keep you posted on how it goes......