P
Welcome to the forum.
In case you are not aware, your real name appears to be showing in the forum, if you want to change this then follow the instructions in the following FAQ
My full name is showing, how can I stop it?
There are two issues;
First, it is not your marital status that is considered but whether you are considered to be living together or not as a couple.
Secondly, the issue is only relevant to means test benefits such as ESA(IR), UC, IS or HB, there are others.
DLA or PIP is not means tested so there will be no issue.
If you are both only receiving Contribution Based ESA, then this is not means tested and there will be no issue.
If only one of you is receiving ESA(IR), either in whole or as a top-up to their ESA(CB) then there ESA will be affected but they should actually see an increase as they become eligible for the couples rate.
If you are both receiving ESA(IR) in whole or in part then one of you is going to have to lose your ESA(IR) (but not any ESA(CB)) as only one person in a couple can receive ESA(IR).
Similar rule exist for HB if you are receiving it.
If you think that you are affected then I would recommend that you get face to face advice as to which options would be financially best for you.
Gordon