The 52-year-old star, who has been dating Randall since last year, have planned to tie the knots in a private ceremony, reported E! online.
According to a source, the marriage "will be private and under the radar."
"They are pretty much married the way they act around each other and the amount of time they share with one another.
"The family connection they all share is very deep. Sandra is all about family values and being down to earth and raising her children with valuable lessons. Bryan shares the same values," the source added.