When asked one time about sleeping arrangements with subsequent children, I shared with a group about our sleeping arrangements. We have a family bed, which at this time, includes two adults and four children. A young mother exclaimed how she would never have that many children in her bed. That is her perogative. It works for us.
Six people in a family bed together does sound like a lot. Squished onto a king size bed, I doubt we would be comfortable. However, rather than arbitrarily try to fit our family and its needs to commercially and socially expected bed sizes, we have fit our bed size to our family’s needs. We had a king size bed before having a child. When our first was born, it was only natural that he sleep with us. Before our second child was born, we decided to add on to the bed so that everyone would have plenty of room. We found a great deal on a queen size bed, and the next thing we knew, we had a king/queen combination. This lasted us for quite a while, including a third child.
When our oldest turned seven, and I was pregnant with our fourth baby, we found a need to add on again. Our seven year old was kicking in his sleep, and no one enjoyed sleeping next to him. Many families would have decided it was time to make him sleep on his own. However, we had decided that our children would decide on their own when they were ready to move out of the family bed. We know that they will eventually; they won’t still sleep with us by the time they are ready for college.
Faced with our son’s desire to continue with the family bed and a number of individuals who preferred not to sleep next to him, I asked him if he would like a space of his own. We had a twin mattress in our storage room. He was delighted with the idea, and we added the twin bed next to our king/queen combo. We didn’t have a boxspring for the twin, as it was designed for a bunkbed, so his bed is at a lower level than the rest. It allows him to remain in the family bedroom while giving him a little space of his own in a way that any kicking won’t bother anyone else.
Our king/queen/twin combo may seem like a monster bed, but it works for us.
living peacefully with children 
We have 2 adults and 2 kids and a handful of cats – a twin bed and a king (our bedroom is too small for more). I completely love it. Yay monster bed – I love the term, perhaps way more than “family bed”.
That is so nice that you have a master bedroom big enough to accomodate the “monster bed”! 🙂