I tried "What do you call your grandfather" knowing that Cómo se llama usually means "what is the name....", but asking a person what they call a grand parent seems like a common question. Our grand daughter calls me 'granpa and my wife lita. SO how would a person ask the name they use for their grandparent?
I had the same thought, but after considering it, realized that the problem comes from the mix of conjugations "se llama" and "tu". I think if we wanted to ask "What do you call your grandfather" we would need to change "se llama" to "te llamas" If we leave it as "cómo se llama" I think it more directly translates to "What is subject called?" because the conjugation is not second person familiar (although it would technically work for second person formal, but I think that is unusual and with a lack of contradictory context we are expected to stick with the traditional translation). I'm not sure if I explained myself very well, but those are my thoughts.
(And btw, I tried it, and "What is your grandfather called?" was accepted)
I may flub this response both because I am tired and my grasp of Spanish and English grammar is tenuous compared to many other users. The construction 'reflexive pronoun' + 'llamar' is a pronominal verb that translates to 'to be named' or 'to be called.' So,
"¿Cómo te llamas tu abuelo?" = "What is your name your grandfather?"
I think to say what RobertKinzie was trying to say, you need to just use llamar as a transitive verb without the reflexive pronoun.
"¿Cómo llamas tu abuelo?" (Not sure if this would be "What do you call your grandfather?" or "How do you call your grandfather?")
"¿Cuál llamas tu abuelo?"
Maybe you need to use "apodo" or "sobrenombre" (nickname) to avoid confusion.
that is half knowlegde and not really correct
llamar means to call (somebody/something) and NOT to BE called ...it is not "how are you called", but rather "how do you call yourself" ..it does not work for things, as they can´t call themself... even if it is technically correct for humans and their names (only!) ...this is not what you think of, if you think in spanish language
cómo te llamas - how do you call yourself
cómo te llamas tu abuelo - how do you call yourself your grandfather
cuál llamas tu abuelo - which (one) do you call your grandfather
cuál es nombre tu abuelo - which (one) is the name of your grandfather
here comes the important part:
cómo TE llamas TU abuelo - how do you call yourself your grandfather
to avoid the conflict of "TE ... TU" the spanish languange changes the TE towards SE gives it the singular 3. and so it changes to
Cómo se llama tu abuelo - it can not really be proper translated as this is a thought only possible in spanish language, but the closest is - how do(s) [all/anyone/everyone] call your grandfather ...it does still not mean "how is he called" if you think in spanish language.. but if you think in english language, then it means "how is he called", but keep in mind that this phrase only works for objects that can call themself
"Se" is a reflexive pronoun that can mean yourself (formal), himself, herself, it, you all, or themselves. (It is the reflexive pronoun that corresponds to the subject pronouns usted, él, ella, it (no Spanish translation), ustedes, ellos, or ellas.)
'Reflexive pronoun' + 'llamar' is a pronominal verb meaning 'to be named' or 'to be called.'
Me llamo Juan. = My name is Juan.
¿Cómo te llamas? = What is your name? (literally, How are you called?)
¿Cómo se llama? = What is your(formal)/his/her/it name?
Nos llamamos Salma y Maya. = Our names are Salma and Maya.
¿Cómo se llaman? = What are your/their names?
Duo introduced these phrases in the greetings lesson without diving into the grammar rules to get users familiar with asking someone their name.
Without the reflexive pronoun, llamar means to call.
¿[Tú] llamas tu madre todos los domingos? = Do you call your mother every Sunday?
The indirect object pronouns le and les change to se when followed by the direct object pronouns lo, la, los and las. https://www.spanishdict.com/guide/direct-and-indirect-object-pronouns-in-spanish
DuoLingo is a free service that is offered to help people around the world learn new languages. So if you are unhappy with the program, it doesn't make sense to be angry at them about it considering you are using it for free. Also, the people working at Duo have millions of sentences to proofread and troubleshoot and edit, so you can hardly be surprised when you run into occasional glitches that have not been addressed yet.
You should copy and paste your answer into you post to help other users provide better feedback. Spanishdict.com lists llamarse as a pronominal verb meaning 'to be named' or 'to be called.' However, I believe the reflexive pronoun can only be attached to the end of the infinitive form of the verb or an affirmative imperative form of the verb. You can't use the infinitive form in this sentence because it does not contain another conjugated verb.
Puedes llamarme Jeff o Mexicanfoodfreak. (You can call me Jeff or Mexicanfoodfreak.)