ofc they dont. Do you have the same DNa as your sister or brother? no!
no strictly true, brothers have the same Y chromosome
No, thats not the same thing at all, theres variants in the DNA in chromosomes, we dont even have identicle Y chromosomes. You and i have about 99.99% the same DNA, you and I and a chimp picked randomly from the african savannah have about 99.1 % the same dna, but you, me and the chimp do NOT have 100% the same DNA, no two living creatures above the level of single cell animals have 100% identical DNA, hence they can be individually identified, we are all unique.
The DNA we all have with the LEAST variant is the Mitochondrial DNA transmitted by our mothers to us. Broadly speaking, every single human alive today has a fragment of the mitochondrial DNA from a group of females alive about 200,000 years ago in Africa. These group of women are collectively known as Mitochondrial Eve, and had the original Haplogroup that all humans now have, Haplogroup A.
Because of the more rapid mutation of the Y chromosome, the MRCA (Most Recent Common Ancestor) on the male side, known as Y-Chromosomal Adam, was only about 90,000 years ago.
The single individual human with the most traceable ancestors may be Ghengis Khan. There about 1 million chinese who can show genetic linkage to him.