Yes he can.
If he was just neutered today:
Leash walks only so he can urinate and defecate. If he runs around he risks breaking sutures/glue.
If he was neutered a few days ago:
Also leash walks only until sutures fully healed
Remember to keep the e-collar on!
The effect of it would be its her brother it runs in her family of the syndrome so of course there would be a most likely chance of her first son getting it because its her first son and the sysndrome is in her brother which is blood and her son which is blood. he may not get the full effect but he would get maybe the whole effect or some of the effect.
B- maintaining a stable internal environment.
The skin isnt part of the excretory system