“Getting ready to be a big brother,” she added.
The star then gave a shout out to her daughter, writing: “Congratulations Morgan and Ryan. I can't wait for your little family to grow.”
Enthusiastic fans were quick to take to Instagram to congratulate Lisa on her news, with one fan writing: “That's wonderful news, Lisa. Flynn will be an awesome big brother.”
“Congratulations to you Lisa and your beautiful family! Look forward to the journey through your eyes!” another person stated.
A third person added: “Wow congratulations Lisa, can’t wait to meet another beautiful little Flynn, congrats to Morgan and Ryan, how exciting.”
Lisa’s exciting baby news comes after the star recently gushed over her over hubby Mark Tabone in throwback post to celebrate their anniversary.
“Two years ago, this beautiful day happened... I love you more today than yesterday, and will love you more tomorrow than today,” Lisa began.
“My thoughtful, kind, loving, funny Mark... and fabulous on the tools... I think I’ll keep you.”