This question must be read together with your earlier question “How to get my husband to satisfy me? in order to get the proper context of this question.
You got 16 Answers and many more comments for that question. Congrats. It is a record of sorts on AA. You had told us in detail that you live with your husband, father-in-law and 2 brothers-in-law. You were married for 3 years and your husband did not have sex with you and so you felt the need for having sex with others.
This was bound to happen, as you must have had this on your mind for some time. Sex is a powerful human body need and the mind looks for ways to fulfil this need. You say you will stop at a blow-job, but this may not be possible as the body always craves for more. Presently due to your guilt, you have limited yourself to oral sex, and one can reach orgasm with only oral sex. But soon you will have the craving for vaginal sex. What then?
Have you considered what your husband’s reaction would be, when he finds out that you have been having sex (oral sex is also sex) with his brother? Do not fool yourself that he will never know. He will in time to come. You could be lucky and he may turn a blind eye to what is going on as he is not able to sexually satisfy you or he could get nasty and demand that one of you leave the house. Be prepared for that.
You could also fall in love with your brother-in-law, as he starts treating you well for the sex that you provide him. This will lead to even bigger problems. So think of all the consequences. Rest assured that the sexual intimacy will grow.