I personally wouldn't limit his time with his cousins or other kids as long as he wants to play with them and you like them. My daughters tics were greatly reduced by limiting artificial colors, flavors & preservatives. We also switched to organic meat, milk and other foods when possible. Other things that helped were filtered water and unbleached flour. Read Sheila Roger's book for ideas of environmental triggers and keep a log to find patterns. Interestingly, when her tics were reduced, a couple out of the ordinary fears she had developed also went away.
