I have always wondered about this sad separation and death in the Asplund family but I think there is an explanation as to why it happened.
In the first place, I believe the lifeboat in which Selma, Lillian and Edvin Felix Asplund were rescued was a late
port boat, which explains Carl Sr and 13-year od Filip not being allowed to board. ET, while giving a large margin for alternatives, believes that they were rescued on Lifeboat #10, which
was one of the later portside boats. But IMO Lifeboat #4, in which many others believe the 3 surviving Asplunds were saved, is a greater possibility.
23 years ago Michael Findlay posted this excerpt at the beginning of this thread. He said he had spoken to Lillian Asplund in 1989 and so it is first hand information.
She remembered that her mother got in holding her brother Felix (and had to climb through a window).
To me, the need for Selma, Lillian and Edvin Felix to
go through a window to get into the lifeboat suggests it was
Lifeboat #4. Lightoller was in charge and he would not have allowed Carl Sr or Filip to board for certain ("No more boys!"). As for 9-year old Clarence and 5-year old Carl Jr, there really might not have been time,
especially if the two young boys had clung to their father in fear and showed reluctance to board. There was not much time and Lightoller was not the sort of man who would have tried to persuade or even wait for the boys to join their mother and siblings in the boat. With all concerned increasingly edgy and pushed for time, Lightoller simply could have given the order to lower away when the two boys did not willingly get on board.
Apparently, the boat lowered so fast that the rest of the children couldn't be dropped in. Mr. Asplund was last seen leading the other boys away from the rail - presumably to find another boat.
If Carl Sr had really told his wife "You go, we will get into one of the other boats", he would have meant exactly that. He might have known or guessed that there were other lifeboats, but the trio had remained on the port side, their only option would have been Collapsible D. But with the crowded chaos around that boat and the need to get through the sailor's cordon, many passengers who would have been allowed could not even get close enough to board (Edith Evans for example). Even if Carl Asplund Sr had tried to emulate Michel Navratil and hand over only the children, they mght not have been willing to leave him and/or terrified by the 3-foot gap between Collapsible D and the side of the ship due to the port list. We must remember that Wilde and Lightoller lowered Collapsible D in a hurry and only half-full because the crowd situation was getting out of hand.
I personally think the 3 Asplund survivors were on Lifeboat #4 for reasons mentioned above and not on Lifeboat #10. Murdoch was in charge of #10 when it was lowered and although it had "40 to 50 people" on board, there certainly was room for Filip, Clarence and Carl Jr and Murdoch would not have stopped the father boarding with his children.