【Offspring】 , 【young】 ,  【progeny】 ,  【issue】 ,  【descendant】 ,  【posterity】  are comparable when they mean those who follow in direct parental line.

【Offspring】 applies to those who are by birth immediately related to a parent; the term does not necessarily apply to human beings, for it may refer to animals or sometimes to plants.

【Young】 is used most often of the 【offspring】 of animals.

【Progeny】 usually applies to the 【offspring】 of a father or a mother or of both; the term more often refers to those of human parentage, but it is used occasionally of the 【offspring】 of animals and plants.

In comparison with  【offspring】 , however, it has somewhat extended use, being sometimes applied to those who trace their ancestry more remotely or to those who are the spiritual or intellectual successors of a great man.

【Issue】 , chiefly a legal term, is more abstract than the preceding terms and is used merely to call attention to the fact that a union has or has not reproduced its kind.

【Descendant】 , on the other hand, applies to anyone who has or, in the plural, to all who have a right to claim relationship with a person as an ancestor in direct line; the degree of nearness does not matter, but the relationship of each as child, grandchild, great-grandchild, and so on must exist.

【Posterity】  differs from descendants only in connoting all the descendants of a common ancestor.

The term is also often used of the generations that come after a person, a race, or a people.