Is it just me or do other people feel a pang of jealousy when they see families together?

I have 3 friends, all sisters and all grown up with their own children. They have a brother too. They were all together celebrating their mum’s 75th birthday at the weekend. Parents, grandparents, teenagers and small kids. The full shebang. They all looked so happy together and I thought what pleasure it must be even just preparing for that event. All deciding on what clothes to wear, what venue to pick, what food will we have. Will mum and I try out a fancy new cocktail on the menu. I see their smiling faces all over social media projecting their family fun onto everyone. I really don’t feel angry or bitter, only a sense of longing to have that with my family.