I have no romantic experience with other ISFJ's. I do have a close friend I believe to be ISFJ though. We get along great. We can talk about almost anything and can trust each other. I found this chart on massmatch.com and it shows the different personalities that are compatible with ISFJ's.
Best types for a relationship: ISFJ, ENFJ, ESTJ
Possible types for a relationship: ESFJ, ESTP, ISFP, INFJ, INFP, ESFP, ISTJ, ISFP
Least likely types for a relationship: ENTJ, INTJ, ENTP, INTP, ENFP