Well Spouse Affair

Someone I know who looks to me for advice is sleeping with a someone whose spouse is a quadriplegic. I know how hard it is to care for a disabled spouse since I have one not near that disabled. I think adultery is wrong, but I also know that caring for someone with a disability is beyond hard. The single person seems to be well centered but did say the married person mentioned being together some day down the road. I think the single person should look for a long term relationship and not wait around. If they want to keep seeing each other, I don't object but know on some level it is not right. I just don't want them to be found out since it could cause a lot of problems all the way around.