Hi Arlene! Very exciting contemplating a sibling for Rambo.
If he likes being around other dogs, chances are he will enjoy the company. I have to say though, my 2 boys are not self-entertainers. They are always at my feet, together.
They do love having one another though.
My boys are only 1 year apart. The older, Max, has an 'only child' personality. The boys got along instantly, but we did have an adjustment period as Ann described. We had a little bit jealousy and sorting out eating/sleeping arrangements, but it wasn't bad.
Best wishes in making your decision!