Blood Relation is when a person who is related to another by birth rather than by marriage. Persons descended from the same ancestor are said to be Blood Relations.

According to Hindu Succession Act, Two persons are said to be related to each other by full blood when they are descended from a common ancestor by the same wife.
Example: A and B are married to each other and out of their married have children namely C and D. Here C and D are related to each other by full blood.

Two persons are said to be related to each other by half-blood when they are descended from a common ancestor but by different wives.
Example: A (husband) and B (Wife) have a child namely C. B predeceased or gave divorce to A and subsequently A marries D and out of this marriage have a child namely E. Here C and E are related to each other by half blood

Two person are said to be related to each other by uterine blood when they are descended from a common ancestress but different husbands.
Example: A (husband) and B (Wife) have a child namely C. A predeceased or gave divorce to B and subsequently B marries D and out of this marriage have a child namely E. Here C and E are related to each other by uterine blood