Talk to Pediatrician on Skin Vitiligo

I have two sons first one is 3 years 3 months the second one is 10 months...three months back my elder son has developed a white patch over the eyelid...i took him to dermatologist and he diagnosed it as Vitiligo...n prescribed treatment with provate and protopic...its been 2 months now that am applying those topical creams provatebi applied for two weeks, then protopic am applying uptil now...the white patch over my sons eye is shrinked alot...and hopefully will disappear for now... But now i have found that there is a tny white spot appeared on my youngest son cheek...am scared coz it too look like vitiligo...i don’t understand why is this happening to my kids...plz help what should i do...and is this possible that my both kids suffering from vitiligo?