Until gay marriage became legal lesbians and gay men had no legal status if they lost their partner or if a family decided to cut off the surviving partner. Registering a gay marriage will give you next of kin status and important tax protection.
If you have already made a will prior to your gay marriage then it is very likely that your Will may not be valid unless you have specifically made reference to your gay marriage.
In the UK if you have entered into a civil partnership and you die without a valid Will then the first £125,000 of your assets will go to your next of kin that is your surviving civil partner.
If you leave more than £125,000 and have children then your partner will get £125,000 and a life interest in half of the remainder, your children would get the rest. If you have no children but your parents are alive your partner would get £200,000 and half of the excess amount. The rest would go to your parents. Brothers and sisters will only inherit what the parents would have received if the parents are deceased. Please note these figures are under review.
Other Useful Articles:
What is Intestacy?
Prenuptials
After Your Wedding