The definition of families and relationships has changed over the years but I think that the definition of love is still the same. The best definition I have found is in the Bible - Love is patient; kind; does not envy; does not boast; it is not proud; it does not dishonour others; it's not self-seeking and doesn't get angry easily; it doesn't keep a grudge-list; it is happy with good, and when good things happen to others; it protects; trusts; hopes, perseveres; and love never fails.
The real meaning of love is an unconditional presence given to another person that is nonjudgmental, open-minded, and considerate of the other’s needs. Love doesn’t grow bitter. Love is patient. Love is truly listening and giving ones heart to someone else. Whether the definition has changed is a difficult question. People can put their own spins on what real love means to them and go off of that in their relationships. The definition nowadays can be based on a variety of things and the validity of meaning can only be based on the standards one is using to measure it.