It is not illegal to have children sleep in the parents bed as long as its a non-sexual. In many cultures, it's considered more than acceptable to have kids welcome into the bed of the parents.
Once a child moves toward puberty, the communal bed should be discontinued.
I'm not saying that if there are other problems in the home that Child Protective Services might not look at you funny but its not technically illegal.
Personally it wouldn't be my choice but its also not my culture.