You can credit the SQ flights to Virgin but not the Aegean flights.
Do you want to earn status with Star Alliance? Or just want to earn points that you'll be able to redeem for future flights?
This website may help with determining your options:
Find the best frequent flyer program for every flight. Where to Credit shows you the number of miles you earn on any frequent flyer program!
www.wheretocredit.com
If you're doing at least 4 flights on Aegean and the SQ flights are in Biz, you might be able to earn enough miles with Aegean to get status, assuming you're flying round trip. (You'd need to check your fare classes to see what you'll earn.) But if you're not flying much on Star Alliance in the future, that's probably not very useful.
You can credit flights with both SQ and Aegean to any Star Alliance program. KrisFlyer miles can be used for Virgin flights. Again, might be worth checking what you'd earn to make sure it would be enough miles to redeem for something useful.