son has a right by birth

Arunachala Mudaliar vs. Muruganatha Mudaliar, 

AIR 1953 SC 495:

"According to Mitakshara, the son has a right by birth in his father's and grandfather's estate, but a distinction is made in this respect by Mitakshara itself. In the ancestral or grandfather's property in the hands of the father, the son has equal right with his father, while in the self-acquired property of the father, his rights are unequal by reason of the father having an independent power over or predominant interest in the same."

The principle is that the son gets a right by birth in the father's property, whether it is ancestral or self-acquired. However while the son's right actually to dispose of the share is unobstructed when the father's properly is ancestral, it is obstructed when it is self-acquired by the father's full rights of disposal. 

But this distinction does not affect the factum of the son's getting a right at the very moment of his birth in all the property owned by the father. Once this is understood, succession, even to the father's self-acquired property, is by survivorship, properly called, and not by inheritance, Confusion is sometimes created by the loose use of the word "inheritance' as also by some passages cited out of context from old Privy Council judgments, and also in some of the translations of the old texts, where the word 'pitriam' is translated without clear reference to whether it is 'pitriam' in respect of the son who may succeed, or in respect of the father who owns the property, In the one case, it would mean all the property of the father, while in the other only that property which is ancestral in the father's hand. Be that as it may, the pronouncement of the Supreme Court makes the principle underlying the Oudh ruling quite untenable. Actually, even in Oudh the 1930 ruling is no more sound law. 

The later decision of the Allahabad High Court in Mt. Ram Dei v. Mt. Gyarsi, AIR 1949 All 545 clearly lays down: 'The self-acquired property of a Hindu father which his sons who were joint with him get on his death is in their hands joint family properly.' 20 The same problem has been discussed at some length in Girdharilal v. Fatehchand, (S) AIR 1955 Madh B 148:

"It is settled that a son has a right by birth in the father's self-acquired property. It follows as a necessary consequence that the property is unobstructed heritage devolving by survivorship and that if the self-acquired properly has been not disposed of by the father during his lifetime on his death, the undivided sons and grandsons would take the property to the exclusion of the separated sons or grandsons."