Can't wait for Lil Bro to grow up

Last night, Timo told me he loved his lil bro.  He kept hugging the poor lil chap's head, & pinching his cheeks.  I allowed that to go on, whilst keeping a watchful eye on them.  Was fearful that he'll break the small guy's neck or something.  Anyway, it was quite a sweet sight.  He also kept grumbling to me that Jo was taking too long to grow up.  Asked me several times when his lil bro will grow up & play with him.  They are 4 years apart.  Did we make the gap too big?  And I wonder too, should we have another, or are these 2 boys it?