Was Arjuna really the son of Indra?

Arjuna was son of Indra according to Mahabharata composed by Vyasadeva. But he was mantra prasad not biological son of Indra. I think as nowadays people worship gods to fulfill their wishes and make efforts themselves and if their wishes are completed, they start to say that God gave them this thing and that thing. I think same conditions followed in birth of Pandavas. Otherwise you youself think, “How is it possible that a person from other Planet may come on other Planet to make relationship with a lady and think about that person who is king of heaven and may have a lot of wives and all luxury thingy for entertainment why’ll he come on earth for this thing?”

In Mahabharat, it has written nowhere that god Indra made physical relationship with Kunti. According to me, Arjun was equal to Indra in valour and bravery but many times I have found that Arjun was much braver than any living soul of that time except tridev and Lord Krishna. Maybe due to this reason people may start to assume him son of Indra. Sometimes I feel that Arjun was test tube baby and there was any test tube specialist named Indra who helped Pandu and Kunti in birth of Arjun or maybe that Dr Indra may have helped Pandu in inserting his sperm into Kunti. Whatever maybe but I don’t accept this thing that Arjun was biological son of Indra.

I hope that my answer will satisfy you.