Having RA factor positivity and having rheumatoid arthritis are two distinct things. Yes you can definitely get married and have children. There is definitely higher risk of having rheumatoid arthritis in children of affected parents as compared to normal individuals but they may or may not develop rheumatoid arthritis. If you take proper treatment under a Rheumatologist and keep your disease in remission, then it will not affect your couple life. Otherwise it is difficult to lead a quality life with painful, swollen and deformed joints. There are matters regarding family planning and contraception that will be best explained to you by your Rheumatologist.