♥ was the symbol for the organ “heart” which, originally, scientists thought off as the center of thinking and emotions. much later on, did they actually realize that that center for thinking/emotions was actually the “brain”. but since that was a lot later, the “heart” idea still stuck in phrases and daily conversation. love is a emotion, which is probably why it is related to the “heart” (organ). as for the ♥ symbol itself for the organ, well the organ kind of looks like that symbol, so that’s how that came about.
Disclaimer – I have not studied symbolism in depth. This is just how I think heart became the symbol for love based on my studies of the history of medicine.
@ allie – your link won’t load for me for some reason (the header and background of the page shows up, but not the actual content)