assalamu alaykum, if the groom is financially poor is it allowed for him to ask financial help from the brides family to arrange walima party jointly (by the both family)?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

You should know, first of all, that the marriage banquet is observed by the husband and that is recommended according to the Majority of jurists, which is the opinion we view as the most prepoderant. For more information, kindly consult the two Fatawa 98859 and 133125. According to the opinion that it is obligatory, giving it is conditioned on the husband’s ability – a point understood from the Saying of Allah, the Exalted (what means): {Allah does not charge a soul except [according to] what He has given it.} [Quran, 65:7] The husband can give the banquet in light of his ability to do so, since there is no fixed limit to be followed herein. This is supported by Prophet Muhammad’s instruction to ʿAbdurr-Rrahman ibn ʿAwf “Hold a wedding feast, even if only with a sheep.” He himself, then got married to Safiyyah gave a wedding marriage with Hais. Anas narrated that the Messenger of Allah set Safiyyah free and married her, making her freedom her dower, and he held a wedding-feast for her with Hais (A dish made of dates mixed with clarified butter and dried curd, kneaded and rubbed together. Sometimes flour was added.)” [Al-Bukhaari]

As far as begging is concerned, it is prohibited unless for a necessity or a need. This is supported by the Hadith narrated by Imam Muslim in his Saheeh on the authority of ʿAbd Allah that the Prophet said, “If one of you would keep begging (of people) until he meets Allah (on the Day of Resurrection) his face will be without a shred of flesh.” This ruling is also applicable on the part of the husband towards his relatives by marriage, since this might make them scorn him.

As far as the topic of “begging” is concerned, Ibn Hajar in his Fat'h Al-Baari said, “The Shafiʿi scholars are of the opinion that it (i.e., begging) is permissible since it is an allowable request, and thus is similar to Al-ʿAriyah (i.e., borrowed items). They interpreted the Hadiths on prohibiting this act in light of asking for money from the obligatory Zakat even though those who ask do not deserve it. But, An-Nawawi said in Sharh Muslim, 'Scholars agreed on the impermissibility of begging for no need. He (An-Nawawi) commented, 'Our companions differ over the Sharee'ah ruling on the act of begging if done by the financially capable, as follows: - the most authentic opinion is that it is impermissible as understood from the apparent meaning of the Hadeeths; second, it is permissible yet disliked on three conditions: he should not insist on begging; he should not humiliate himself, and he should not cause any harm to the person from whom he begs. So, if any of these conditions are missed, it is unlawful.” So, keeping away from the such act is better for the person since it protects his honor.

Allah knows best.