Jaime and Cersei relationship

[BridgeofFire]

In ASoS Jaime’s chapter, Martin writes 

Quote

Long before his sister’s flowering or the advent of his own manhood, they had seen mares and stallions in the fields and dogs and bitches in the kennels and played at doing the same. 

I was wondering what was the nature of their relationship at this time. By this I mean was it really intimate, because what ever their mother’s maid caught them doing obviously disturbed her. 

[redwolf@winterhell]

This is from a wiki of ice and fire; Jamie Lannister;

Cersei and Jaime slept together in the same bed when they were very young, and even went as far as to experiment together in a sexual manner at a young age. 

They did have sexual relations when they were young. O maid caught them together and told Johanna. Johann put a guard outside Cersei's door and moved Jaime to the other side of the castle.