Was the sim definately linked to your account?Check on your spread giffgaff page then more on your recruits.It'll tell you when your brother activated his sim if it was linked to your account.
If the sim was linked to your account,you'll receive 500 payback points which will be paid out in June.
Did your brother get his £5? if so you should have got £5 added as credit to your account , the 500 points will show as points.
A lot of users were missing recruits in January, if yours shows in my recruits but you got no points ask an agent to check.
If you are talking about the £5 for signing up a new member within 6 weeks of you joining this £5 is usually paid within 5 days,and is usually paid out on a Tuesday or a Thursday...Please remember you only get this £5 for 1 recruit,not every recruit.