After more than 2 year wait, I’ve received a biometrics appointment letter from AIMA. However this appointment is only for the primary applicant, the wife and children who are also on the application haven’t been invited.
Is it a common practice for AIMA to separate family members?
Having each family member traveling for appointment individually on different dates is a logistical nightmare.
Is it possible to request that all family gets the appointment at the same time?
Unfortunately
Answer: Yes
Answer: No
I was also told this story a few months ago, and trust the source that it’s true…
That’s so Portuguese!.. 
I’ve seen people report success a couple of times I believe (especially where it involved children), but it’s a looong shot.
But definitely plan on attending your originally assigned appointment. Missing it is likely to cause serious delays.
I was able to get 3 of 4 to the appointment . My daughter could have also made it but could not due to work issues. Using an attorney was life saving.
It’s possible the other way round (child invited, parent not), as we did it. My husband had fallen in to a black hole as he’d missed his first appointment. When our daughter was invited our lawyer was able to persuade AIMA to do my husband at the same time, as she couldn’t travel alone to her appointment so he’d be going anyway. This seems hit and miss though. Worth a try.
My first appointment was all together, but this was at the start of covid and appointments were easy. I did not want to pull the out of school as it was a Wednesday and foolishly thought that they could just reschedule for school holidays. Then the system got f■■■ed and it took me 6 months to get my appointment. Wife was a year later and children another 1.5 years later. My attorney thinks that they do this so that you have to spend more money visiting Portugal. When my wife went for hers, she landed at 8PM, did the appointment at 9AM the next day and was in London for a late lunch just to spite them.
Since my family was with me for my appointment and I knew that there would be significant cost to return for their appointments, I pulled out a fistful of Euros (maybe 1000) and asked about expediting the process for the rest of the family. Before the SEF agent really understood what I was asking, my attorney, who is Brazilian, grabbed the money and said you can’t do that here and they will deny my visa. Do not recommend trying this route.
Hmm… attempting to bribe a public official - that’s a 5 to 8 year prison term. You have a good lawyer…
In the US, you can pay extra to expedite certain things like passport applications. But probably better to ask first before shoving cash in their face 
Notably, you pay through official channels, not cash to the clerk
My lawyer got all four of us together.