Once you have lived many decades in a role that aligns with your birth sex, making any kind of announcement can be akin to throwing a live hand grenade into a room. Your family members may have had no inkling of your true identity and this feels to them like a betrayal. No one is more likely to feel this way than the spouse who thinks she knew her husband.
At this point, coming out can be a Catch 22 scenario where every move in the direction of authenticity is a distancing from a family who will feel naturally betrayed. Things can get ugly and complicated and the trans person may find themselves entirely alone after the dust has cleared. No advice can help solve this situation simply because it will pit the desire of the person to be themselves against the wishes of a family who will likely at first resist such drastic change. That tug of war can often eat the trans person inside from the angst and guilt of having kept this a secret so long. It will test their will to be themselves against appeasing the family they love.
There are no easy winners here and the outcome will depend on a great many factors that the trans person cannot fathom before taking that huge step to divulge. It is like jumping off a cliff into the void and praying that the landing is not as harsh as imagined.
Like a lot of situations in this life, it will test all parties involved regarding what is the true meaning of love.