Yes. You can love two or more people at the same time.
What we call love (sometimes it’ just chemistry, attraction or lust) happens at a sub-conscious level. Sometimes we don’t know why, how and when it happens, we just know we feel this very strong pull towards someone and they are all we think about.
A relationship is different from love. A relationship is a conscious choice to be with someone; a practical decision we make based on so many factors including how attractive we find them, how well we get along, shared values, dreams and interests, mental compatibility, financial security, etc.
In an ideal world, love comes first and is closely followed by a relationship. But sometimes a relationship comes first followed by love (as in arranged marriages).
In a not so ideal world, we can love someone but not want a relationship with them, and we can be in a relationship with someone we do not love.
In other words, who we love and why is on most part not up to us. But WHO we choose to be in a relationship with, WHY we choose that one person over all the others, HOW we get into a relationship with them and even WHEN we get into a relationship is all up to us. That is why they say relationships are hard work.
We need many different kinds of relationships in our lives because one person can not meet all our social, intellectual, psychological and emotional needs. A committed relationship however, is a (romantic) decision to “forsake all the others” to be with this one person. It is both ability and willingness to work on sharing your lives.