Perhaps if you gave more info you would get some answers! You said they had 10 children.... is this the family as found in the 1910 Cleveland Census ?
John Marencic 31
Mary Marencic 29
John Marencic 8
Mary Marencic 5
Frances Marencic 3
Rosie Marencic 2
Ignatz Marencic 1
The census indicates that Mary and John (Jr) arr in the US 1904 and John Sr 1903
Finding info on such common surnames without doing your homework in the US first is like looking for a needle in a haystack!
How do you know they came from Ljubljana?
Also Mary is an English spelling and would not be found in Slovenia. Perhaps it was Mary. John may have been Janez, Johan or maybe Ivan.
Could this be that family shown in the census?
Name: Maria MARINCIC age 22
traveling with Johan MARINCIC ag2
Arrival Date: 15 Jun 1904
Ship Name: Kaiser Wilhelm der Grosse
Former residence Lahovec or Lakovec
Destination to husband/father John MARINCIC at Newburgh #50 Cleveland Ohio
They were detained at Ellis Island until the 17 as her husband was telegraphed to send money and they then went by RR to Cleveland
Have you checked records at the Slovenian parishes in Cleveland?
Croatian Heritage Museum