  We describe full-coupled-channel ab initio calculations among the octet
baryons for S=-2 s-shell hypernuclei,_{LambdaLambda}^4H,_{LambdaLambda}^5H
and_{LambdaLambda}^6He. The wave function includes Lambda Lambda, Lambda Sigma,
N Xi, and Sigma Sigma channels. Minnesota NN, D2^\prime YN and Nijmegen model D
simulated YY interactions are used. This is the first attempt to explore the
few-body problem of the full-coupled channel scheme for A=4-6, S=-2
multistrangeness hypernuclear systems. Bound state solutions of the Lambda
Lambda hypernuclei,_{LambdaLambda}^4H,_{LambdaLambda}^5H and
_{LambdaLambda}^6He, are obtained.
