SSI Reduction with Postal Federal Pension



I wanted to know if SSI benefits would be reduced someone on SSI (Age of 54 years old) was to marry someone that has only worked for the United States Postal Service and only receives a Pension from the work done with the Postal service)? (Age of Retired Postal work with the Federal Pension is 68 years old and has been retired for 10 years. Has no other income, i.e SSA, Stocks, Property, ect)

Both live in the State of IL, if that makes a difference.

Not sure if the the 2nd question is for this section:

How long if there is a minimum time, frame do these two people need to be married for the one on SSI to receive the Postal workers Federal Pension in there event that they passed away?

Retired Postal work has never been married and has no kids. Only has one sibling that is in their 70's. No parents that are alive.

SSI person has never been married and only has no kids.

Thanks for any advice.