Both my mother and sister are likely ISFPs. There are some interesting relationships between the INFP and ISFP since they share a dominant function. An ISFP with a strongly developed tertiary Ni or an INFP with a strong tertiary Si can difficult to distinguish. I'm pretty sure my sister would test as an ISFP right now because we've had discussions where she talks about preferring concrete thinking. She has tested as INFP, but later has said she thinks she is a Sensor, but doesn't buy into MBTI much. She is a visual artist and her husband has tested as an ESFJ.
I believe the ISFP is described as the kindest of all the types.