In the absence of an identical twin, other siblings, such as those who share identical HLA genes, usually provide the closest HLA match.
(those; share; identical HLA genes) (other siblings, such as those; provide; the closest HLA match; L:In the absence of an identical twin; T:usually)
those other siblings, such as those
share provide
identical HLA genes
the closest HLA match L:In the absence of an identical twin T:usually