  Many insurance products and pension plans provide benefits which are related
to couples, and thus under influence of the survival status of two lives. Some
studies show the future lifetime of couples is correlated. Three reasons are
available to confirm this fact: (1) catastrophe events that affect both lives,
(2) the impact of spousal death and (3) the long-term association due to common
life style. Dependence between lifetimes of couples could have a financial
impact on insurance companies and pension plans providers. In this paper, we
use a health index called physiological age in a Markov process context by that
we model aging process of joint and last survivor statuses. Under this model,
future joint lifetime of couples follows a bivariate phase-type distribution.
The model has physical interpretation and closed-form expressions for actuarial
quantities and owns tractable computation for the other ones. We use the model
to pricing products relevant to couples annuities and life insurances.
