Re: Have got my son a s3 mini and samsung 3 tab can he use the same sim card
The tab uses a microSIM (probably - there are a few TAB3 models), the S3 mini uses a miniSIM. Register the smaller one. Then get a set of SIM adapters (I got a set on eBay for about $1.25 including shipping, and I overpaid.) When you want to use the S3, put the SIM into the mini adapter, then into the S3.
(If you have a tab that uses the same size SIM as the S3, register either one, use that one in either device and keep the other one as a wall decoration. [Most carriers will replace a bad SIM for free - they cost the carrier a few cents.] Even independent dealers get them for free.)