Can a guy be in a relationship amd still have true Feelings for an longterm ex?

Can a guy in a relationship have feelings for an ex but distance himself at times when he feel he getting strong. Guy known for over 20years one minute all over me , physically and texting then he back off. He says he have feelings and it's something we been around all this time but why the back and forth actions by him.
Can a guy be in a relationship amd still have true Feelings for an longterm ex?
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