Shoko,
They do say that the reward for work well done is more work to do well! Having researched what you found so far, I have come up with more family members, who are the children of Thomas (61) and Susan (54) Bartlett, who you found in Almer in 1851. Theses are:
James Bartlett (b. Almer 1821)
Samuel Bartlett (b. Almer 1825)
Thomas Bartlett (b. Almer 1828)
All were in Almer in 1841 but had left home by 1851, when only Robert and Elizabeth were with their parents. Samuel was in Sturminster Marshall in 1871. Could you check please whether they were still in the Morden/Almer area in 1851.
Many thanks,
Terry