TMZ reports.

The world's oldest conjoined twins Lori & George Schappell have died -- according to online obituaries.

The twins passed at a hospital in Pennsylvania ... though the exact cause of their death, reportedly last Sunday, has not been disclosed.

Lori & George were born in 1961 ... fused partially at the skull, and sharing 30% of their brains, the parietal and frontal lobes.

Despite predictions the twins wouldn't live past 30, they beat the odds to live more than twice that long.

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I remember them on Springer and other places in the 90s a lot. RIP