rats that know each other, cage cages?

Question
My oldest rat Mickey died a few days ago. I think his brother Marnix, (1
month younger) wants to be with my other 2 rats, Teevy and Nunu. They are
not brothers.  Nunu seems afraid of Marnix, but Teevy went on the offence.  
The 2 boys play fight a lot. Do you think I should get them neutered before
trying to have them all in the same cage? Marnix is almost 2 and the littler
guys are about 8 months.

Answer
Its hard to say really...its tougher to get older males with younger rats and your bucks are at the prime age of hormones rising. This is puberty and sometimes aggression issues set in but they often outgrow them.   I have had two rats neutered out of all the males I have owned and continue to own.  Those two rats bit me and each other big time and once fixed, they were sweethearts.  I would let their cage near each other for a few days and slowly let them sniff each other while holding the other one.   In a neutral territory, let them meet but first sign of true aggression such as standing on hind legs, circling and hissing, take them apart.  If you have the funds for it and a great vet skilled in rat surgery, I say neuter the bucks but let the 2 year old be.  This is ONLY after they dont seem to get along.  
You can also look to adopt a spayed older female for the 2 yr old. Males tend to take to a spayed female really easy.