Putra means someone tide you over from the Narak called पुत्रं (Puta).

There are 12 types of Putras(Son) according to Manu Smriti Which are Auras, Kshetrak, Dattak, Goodhhotpann, Apviddh, Kaneen, Sahodadh, Kreet, Punarbhava, Swaydutt and Shauddh.

Auras putra is someone who is born from Wife and is considered best among all these according to Manu.

It is said in Manusmiriti.

"पुन्नाम्नो नरकाद् यस्मात् त्रायते पितरं सुतः ।"

Someone who can tide over parents from Naraka(sufferings) called Punnam is Son.

Three type of son are mentioned in Garud Purana Uttama, Madhyama, and Nimna. Uttama, Madhyama and Nimna can be called Suputra, Putra & Kuputra respectively.

It is called that there is no sense of accumulation of wealth if the Putra is Kuputra.

In current times 3 more types of Putras are included in this which are Beta(which will take you money by deviding (Baant), Ladka which will occupy you wealth by fighting(Ladkar) and the last Son who will put you is miserable condition. This is normal language.

There are four type of Son mentiooned in our scriptures which are Hrinanubandh( In debt), Shatru(enemy), Udasin(Neutral) and Sevak Putra(dedicated to serve). among the above the Sevak Putra has been considered best.

According to Mahabharta Eldest son is called Jyeshtha.
Son is someone who makes parent attain all type of happines including materialistic and spiritual. Someone who complete their wishes after understanding. Someone who can sacrifice his life for the happiness of his parents.

In Ramayana when meghnad was asked why he fought against Narayana? even after knowing that Ram is himself Narayana. He replied I have learned from Ram that a son should sacrifice everything for Father.

Now it's up to you which type of Putra(Son) you become which Putra Dharma you follow, because it doesn't take time to become Pita(Father) & Pitra(Ancestor) from Putra(Son).